The present invention pertains to a ball-and-socket joint, preferably for motor vehicle suspensions or steering mechanisms of motor vehicles with a joint housing and a pivot pin, which is mounted rotatably and deflectably in a one-part or multipart bearing shell by means of a spherical bearing surface, wherein the bearing shell is in turn fixed in the joint housing and wherein the joint housing or the pivot pin is fixed against the vehicle suspension in an electrically insulated manner.
Ball-and-socket joints of this type have been known for a long time and are used in large numbers especially in the automotive industry. The ball-and-socket joints installed in a motor vehicle are subject to natural wear due to corresponding stress during the operation of the motor vehicle. The wear limit and the service life of a ball-and-socket joint is reached when the bearing shell arranged between the pivot pin and the housing can no longer assume its bearing function over a large area or partially as a consequence of its wear or other abrasion. Increased wear is frequently the consequence of leaky sealing systems, i.e., for instance, when the sealing bellows was damaged and moisture or contaminants were able to penetrate directly into the interior of the joint as a consequence of this. If the bearing shell is worn off to such an extent, the pivot pin could ultimately even become completely separated from the joint. The function of a ball-and-socket joint whose service life limit has been reached may consequently be substantially limited or lead to total failure, which must not happen especially in the case of ball-and-socket joints used in safety-relevant positions. Such a total failure may have serious consequences for the ability of adjoining components to function and may threaten the life of the user of an affected motor vehicle.
The object of the present invention is therefore to improve a ball-and-socket joint of this type such that the wear on the ball shell of the ball-and-socket joint is indicated by suitable measures, so that timely replacement of the affected ball-and-socket joint can be performed before greater risk potentials develop.
According to the invention, a ball-and-socket joint, preferably for vehicle suspensions or steering mechanisms of motor vehicles, is provided with a joint housing and a pivot pin, which is mounted rotatably and deflectably in a one-part or multipart bearing shell by means of a spherical bearing surface. The bearing shell is in turn fixed in the joint housing. The joint housing or the pivot pin is fixed against the vehicle suspension or the steering mechanism in an electrically insulated manner. Provisions are made for the joint housing and the pivot pin to be connected by means of electrical contacting to a potential difference-measuring unit. The spherical bearing surface of the pivot pin and its corresponding opposite bearing surface in the joint housing are electrically insulated against each other.
This design according to the present invention is such that due to the electrical contact connections between the joint housing and the pivot pin, a potential difference is present in the case of an intact ball-and-socket joint, and this potential difference is eliminated at the moment at which the insulation between the pivot pin and the joint housing is considerably reduced or eliminated as a consequence of wear in an area. This usually happens due to the fact that the bearing shell, which is preferably made of a plastic and is arranged between the pivot pin and the joint housing, is no longer able to assume its insulating function as a consequence of wear in an area. An electrically conductive connection is established at this area between the pivot pin and the joint housing, as a result of which the potential difference between the two components is eliminated. The connected potential difference-measuring means permanently monitors the electrical state of the ball-and-socket joint and in the case of a change in the potential difference, it can activate, e.g., a display device arranged downstream, which can display the necessary repair of the worn ball-and-socket joint to the user of the vehicle.
In addition, the increasing wear of the bearing shell can also be displayed by means of a potential difference-measuring means according to the present invention, so that a replacement of the ball-and-socket joint is also possible already before a metallic contact, i.e., a direct electrical connection.
Within the framework of another special embodiment of the subject of the present invention, the bearing surface of the pivot pin may have an electrically non-conductive coating. This embodiment is necessary when the intercalated bearing shell is unable to assume its insulating function because of a special material selection.